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Physical functioning before knee arthroplasty is not associated with (standardized) preoperative physiotherapy, but is tied to physical functioning 1-year post-surgery: A prospective cohort study
⁎Corresponding author: Tessel F. Bax. tf.bax@nwz.nl
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
and purpose This study investigates whether a (regionally) standardized physiotherapy approach, employing a stepped-care model, can more effectively enhance preoperative physical function in end-stage osteoarthritis (OA) patients undergoing total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) and improve postoperative outcomes, addressing the current gap in understanding the impact of such interventions.
This mono-center observational prospective cohort study followed 216 primary UKA or TKA patients for one-year post-surgery. Preoperative physiotherapy, recorded through self-reported questionnaires, included standardization and treatment frequency details. Physical functioning assessments encompassed quadriceps and hamstrings muscle strength, functional mobility (FM), and range of motion (ROM). Statistical analyses comprised multivariate and single linear regression for both UKA and TKA groups.
Standardized preoperative physiotherapy correlated with superior preoperative extension ROM in TKA patients (B = −3.557, 95 % CI [-.915; −.241]), while less than 10 treatments were associated with superior preoperative extension ROM for both groups (β = −.202, p = .030 and β = −.228, p = .045). No associations were found between location or treatment frequency and preoperative muscle strength or FM. For both groups, preoperative FM, ROM, and muscle strength positively correlated with postoperative levels, except for extension ROM for UKA patients (p = .178).
While adherence to standardized preoperative physiotherapy at an affiliated practice did not significantly correlate with preoperative physical functioning levels, a strong relationship exists between preoperative and one-year postoperative physical functioning levels.
1 Introduction
Osteoarthritis (OA) affects over 1.5 million people in the Netherlands,1 with its prevalence expected to rise significantly, adding an estimated 1,082,000 new cases between 2015 and 2040.2 For individuals with end-stage knee OA who do not achieve relief through conservative management, joint replacement surgeries, such as unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) are commonly performed to alleviate pain and restore mobility.3,4
Conservative OA treatment includes education, exercise therapy, and pain management through analgesics and intra-articular injections. Exercise therapy aims to strengthen the quadriceps and hamstring muscles, enhance functional mobility (FM), and improve the knee joint range of motion (ROM). However, the Dutch physiotherapy guideline for OA indicates that preoperative exercise therapy only modesty improves physical function compared to those who not engaging in such programs. The guideline references studies evaluating exercise programs lasting six to eight weeks,5–11 whereas significant strength gains typically require 6–15 weeks of training.12
A regionally standardized physiotherapy approach, integrated with a stepped-care model and overseen by orthopedic specialists, might provide more effective and personalized care. This approach could start with home exercises and pain management, progressing to more intensive exercise therapy and injections if symptoms persist beyond three months.13
Despite the acknowledged benefits of a stepped-care model,13,14 there is limited evidence on its impact on preoperative physical function just before knee replacement surgery. Studies in other patient groups suggest that optimizing preoperative physical function can reduce complications, shorten hospital stays, and enhance quality of life, consistent with the "better in, better out" principle.15–17
This study aims to investigate the association between regionally standardized preoperative physiotherapy using a stepped-care model and preoperative muscle strength, FM, and ROM in patients with end-stage knee OA, as well as the relationship between preoperative and postoperative physical function outcomes following knee arthroplasty.
2 Methods
2.1 Study design and setting
This mono-center observational cohort study, conducted at a high-volume teaching hospital (The Netherlands), used routinely collected health data. Patients were recruited from January 1, 2020, to June 6, 2023, and followed up for one year post-surgery. Institutional review board approval and informed consent were obtained. The study adhered to STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) and REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) guidelines.
2.2 Participants
Patients scheduled for primary UKA or TKA were assessed preoperatively. Inclusion criteria included end-stage OA (Kellgren-Lawrence grade III/IV), age ≥18, physical capability for testing, and proficiency in Dutch or English. Exclusions were made for recent contralateral knee or ipsilateral/contralateral hip arthroplasty, non-OA knee arthroplasty, or conditions affecting test results, such as neurological disorders.
2.3 Data collection
Baseline characteristics, including gender, age, height, weight, ASA score, surgery duration, and hospital stay, were retrieved from electronic medical records (EMR). Information on preoperative physiotherapy was gathered through a custom self-report questionnaire administered after preoperative assessments. This questionnaire recorded whether participants had received preoperative physiotherapy, the location (affiliated or non-affiliated with the regional care pathway), and the number of sessions, categorized into ranges (e.g., 1–10, 11–20 sessions).
The study's primary endpoints involved assessing quadriceps and hamstring muscle strength using an isokinetic dynamometer, evaluating functional mobility (FM) with the Timed Up and Go (TUG) test, and measuring knee flexion and extension range of motion (ROM) in degrees. Physical function was measured about three weeks before and one year after surgery, with tests performed by trained physiotherapists.
Muscle strength was evaluated utilizing the Biodex® System 3 Pro dynamometer (Biodex Medical Systems, Inc., Biodex Medical Systems, USA), recognized for its solid reliability and validity.18 Isokinetic strength of the quadriceps and hamstrings was assessed with respectively three and 10 repetitions at angular velocities of 60°/s and 180°/s, which represent maximum strength and strength endurance.19 Peak torque values normalized for body weight (Nm/kg) were used for analysis, with measurements exhibiting a coefficient of variance (COV) exceeding 25 % considered unreliable and thus excluded. While a COV below 10 % is customary in sport and exercise science,20 empirical evidence suggests that such thresholds are not practical for patient populations. A higher score on the dynamometer indicates greater isokinetic muscle strength.
The TUG test is a recommended metric for assessing function, balance, and ambulatory capacity in individuals with knee osteoarthritis (OA), and one of the most frequently employed performance-based outcome measures for UKA and TKA.21–24 Time taken to perform the TUG is recorded in seconds, with lower scores signifying enhanced FM.
Knee flexion and extension ROM on the affected side were measured using a long-arm goniometer (Goniometer, Long Arm, Gymna, Belgium) in a supine position, with hyperextension noted as a positive value. Using a long-arm goniometer for ROM assessment has been demonstrated to be valid and reliable at group level.25
2.4 Study size
Based on quadriceps muscle strength, the sample size calculation ensured sufficient power for the study. Using G∗power with α = .05 and 95 % power, and assuming a medium effect size (f2 = .15), a minimum of 119 participants was required. Adjusting for potential dropouts (6.4 % for TKA, 3.4 % for UKA26) and a 15 % voluntary dropout rate, the final sample size was set to 143. The available sample exceeds this number, ensuring adequate power to address the research question effectively.
2.5 Statistical methods
Statistical analysis was performed using IBM SPSS Statistics 27.0 (IBM Corp., Armonk, NY, USA), with significance set at p < .05. Data were first explored to identify outliers and missing values; outliers were examined for potential causes, and missing baseline characteristics were supplemented from EMR when possible. Normality for continuous data was assessed using the Shapiro-Wilk test. Data were considered normally distributed if the W statistic exceeded .90; otherwise, median and interquartile range (IQR) were used. Categorical variables were described with counts and frequencies. Differences between UKA and TKA groups were analyzed using unpaired t-tests, Mann-Whitney U tests, and Chi-squared tests. If differences exist between the two prosthesis groups, each group will be analyzed separately to address the research questions.
Multivariate linear regression models analyzed the impact of (regionally) standardized preoperative physiotherapy on muscle strength, FM, and ROM. Physiotherapy variables were categorized into location (no physiotherapy, affiliated practice, non-affiliated practice) and quantity (none, 1–10 sessions, >10 sessions). Models used the Enter method and reported explained variance (R2), unstandardized regression coefficients (B) with 95 % confidence intervals (CI), standardized coefficients (β), and significance levels. Single linear regressions assessed the relationship between preoperative and postoperative functioning, with preoperative levels predicting postoperative outcomes. Strength measurements were adjusted for body weight, and confounders such as age and sex27 were included based on the change-in-estimate (CIE) criterion.28 Models reported explained variance (R2), unstandardized B with 95 % CI, standardized β, and significance levels.
2.6 Patient involvement statement
Study participants were not involved in the design, conduct, interpretation, or translation of the current research.
2.7 Ethics
This study is classified as a non-WMO study; therefore, the study protocol did not require approval from an Institutional Review Board or Ethics Committee. Participants were informed about the study through written and verbal explanations, detailing the study's purpose, procedures, and their rights. Informed consent was obtained from all participants prior to their inclusion in the study, with consent being documented through signed consent forms.
2.8 Data sharing plan
The data generated and analyzed during this study will be made available upon reasonable request to the corresponding author, in compliance with institutional and ethical guidelines. To ensure participant confidentiality, all shared data will be anonymized, and any identifiable information will be removed. Data will be stored securely and will be accessible to researchers for replication or further analysis for five years following publication. Requests for data access will be evaluated on a case-by-case basis, with priority given to those that align with the original study objectives and methodology.
3 Results
3.1 Participants
A total of 528 patients completed the preoperative assessment. However, the measurements for 130 patients were deemed insufficiently reliable due to a coefficient of variation (COV) exceeding 25 %. For the postoperative assessment, 398 patients were eligible, but measurements for 139 patients were not conducted for unclear reasons. Additionally, 34 patients had unreliable measurements, and 5 patients were excluded for other reasons. Consequently, a total of 216 patients (126 TKA, 90 UKA) were included in the final analysis (see Fig. 1).
Baseline characteristics of the study population are summarized in Table 1. Mean age was 68.1 years (7.5), 53.2 % were female, mean BMI was 28.2 kg/m2 (3.9), and most patients were scored ASA I or II (82.4 %). A total of 101 patients (46.8 %) had preoperative physiotherapy, of which 81.2 % received it at an affiliated practice. The majority (59.4 %) had completed 1–10 treatment sessions. Regarding baseline characteristics, TKA patients were on average just over 2 years older than UKA patients (p = .028). Length of surgery (p < .001) and length of stay (p < .001) were both shorter for UKA patients, who also more frequently underwent preoperative physiotherapy at an affiliated practice (p = .031).
| TKA/UKA | TKA | UKA | p-value | |
| (N = 216) | (n = 126) | (n = 90) | ||
| Age (years)a | 68.1 ± 7.6 | 69.1 ± 7.2 | 66.8 ± 7.9 | .028 |
| Sexb | .764 | |||
| Male | 101 (46.8 %) | 60 (47.6 %) | 41 (45.6 %) | |
| Female | 115 (53.2 %) | 66 (52.4 %) | 49 (54.4 %) | |
| Affected kneeb | .730 | |||
| Left | 105 (48.6 %) | 60 (47.6 %) | 45 (50 %) | |
| Right | 111 (51.4 %) | 66 (52.4 %) | 45 (50 %) | |
| Height (cm)a | 172.9 ± 11.7 | 172.8 ± 12.4 | 173.1 ± 10.6 | .603 |
| Weight (kg)a | 85.3 ± 15.8 | 86.3 ± 15.8 | 83.9 ± 15.9 | .335 |
| BMI (kg/m2)a | 28.2 ± 3.9 | 28.4 ± 3.7 | 27.9 ± 4.1 | .391 |
| ASA scoreb | .279 | |||
| I | 25 (11.6 %) | 11 (8.7 %) | 14 (15.6 %) | |
| II | 153 (70.8 %) | 94 (74.6 %) | 59 (65.6 %) | |
| III | 38 (17.6 %) | 21 (16.7 %) | 17 (18.9 %) | |
| Length of surgery (min)◦ | 62.0 (25.0) | 72.0 (19.0) | 50.0 (19.25) | <.001 |
| Length of stay (hours)◦ | 24.0 (19.0) | 27.0 (23.0) | 19.0 (15.0) | <.001 |
| Preoperative physiotherapyb | .279 | |||
| Yes | 101 (46.8 %) | 55 (43.7 %) | 46 (51.1 %) | |
| No | 115 (53.2 %) | 71 (56.3 %) | 44 (48.9 %) | |
| (If preoperative physiotherapy) – Locationb | .031 | |||
| Affiliated practice | 82 (81.2 %) | 40 (72.7 %) | 42 (91.3 %) | |
| Not affiliated practice | 19 (18.8 %) | 15 (27.3 %) | 4 (8.7 %) | |
| (If preoperative physiotherapy) – Number of treatmentsb | .416 | |||
| 1-10 | 60 (59.4 %) | 28 (51.0 %) | 32 (69.6 %) | |
| 11-20 | 22 (21.8 %) | 14 (25.5 %) | 8 (17.4 %) | |
| 21-30 | 7 (6.9 %) | 5 (9.1 %) | 2 (4.3 %) | |
| 31-40 | 3 (3.0 %) | 2 (3.5 %) | 1 (2.2 %) | |
| >40 | 9 (8.9 %) | 6 (10.9 %) | 3 (6.5 %) | |
3.2 Outcome data
The baseline and one-year postoperative physical function assessment outcomes are summarized in Table 2. At baseline, median time of the TUG was 8.5 (IQR: 3.2) seconds with an average improvement one year post-surgery of 1 s. There was improvement observed between baseline and one year postoperatively in both extensor and flexor strength, both in terms of maximum strength and endurance. At baseline, the UKA group demonstrated more flexion ROM (p = .002). One year postoperatively, the UKA group also performed half a second better on the TUG test (p = .001). Lastly, extension strength at both speeds was significantly higher in the UKA group compared to the TKA group both preoperatively (p = .013 and p = .005) and postoperatively (p < .001 and p = .002).
| Baseline | 95 % Confidence Interval of the Difference | One year post surgery | 95 % Confidence Interval of the Difference | |||||||||||
| TKA/UKA | TKA | UKA | p-value | Lower limit | Upper limit | TKA/UKA | TKA | UKA | p-value | Lower limit | Upper limit | |||
| Functional mobility | ||||||||||||||
| TUG (s) | 8.5 (3.2)◦ | 9.3 ± 3.0a | 8.3 (3.1)◦ | .135 | −.301 | 1.398 | 7.6 (2.4)◦ | 7.8 (2.4)◦ | 7.2 (2.1)◦ | .001 | .296 | 1.398 | ||
| ROM | ||||||||||||||
| Flexion (°)a | 125.0 ± 13.4 | 122.7 ± 13.8 | 128.2 ± 12.3 | .002 | −9.042 | −1.970 | 125.2 ± 12.0 | 124.2 ± 12.1 | 128.2 ± 12.3 | .157 | −5.617 | .915 | ||
| Extension (°) | .0 (8.0)◦ | −.4 ± 6.9a | .0 (5.0)◦ | .456 | −2.593 | .522 | .0 (.0)◦ | .0 (.0)◦ | .0 (.0)◦ | .985 | −4.571 | 1.624 | ||
| Muscle strength | ||||||||||||||
| Peak extension torque (Nm/kg)a | ||||||||||||||
| 60°/s | 86.2 ± 35.9 | 81.1 ± 35.0 | 93.4 ± 36.0 | .013 | −22.074 | −2.584 | 102.3 ± 33.3 | 94.9 ± 31.5 | 112.1 ± 33.2 | <.001 | −26.373 | −7.984 | ||
| 180°/s | 63.0 ± 24.2 | 59.1 ± 22.3 | 77.1 ± 23.4 | .005 | −15.897 | −2.921 | 71.3 ± 22.9 | 66.9 ± 21.5 | 77.1 ± 23.4 | .002 | −16.618 | −3.829 | ||
| Peak flexion torque (Nm/kg)a | ||||||||||||||
| 60°/s | 64.0 ± 26.3 | 61.3 ± 26.7 | 67.8 ± 25.4 | .070 | −13.694 | .540 | 80.3 ± 24.4 | 80.7 ± 24.8 | 79.8 ± 23.9 | .805 | −6.013 | 7.734 | ||
| 180°/s | 53.6 ± 21.5 | 51.5 ± 22.3 | 56.6 ± 20.1 | .084 | −10.828 | .695 | 64.9 ± 19.7 | 64.7 ± 20.1 | 65.2 ± 19.1 | .858 | −6.030 | 5.028 | ||
3.3 Main results
Table 3 presents the results of the regression analyses that explored the correlations between (standardized) preoperative physiotherapy and physical function. A significant association was observed between affiliated practices and extension ROM in TKA patients (β = −.241, p = .009). For this group, engaging in physiotherapy at an affiliated practice indicates an improvement in ROM extension of almost 3.5° (B = −3.557, 95%-CI -.915 to −.241). Conversely, no significant associations were found between TUG performance, flexion ROM, extension strength at both 60°/s and 180°/s and flexion strength at both 60°/s and 180°/s and practice affiliation for both groups. For the amount of physiotherapy treatments, having less than ten treatments is significantly associated with improved extension ROM (β = −.202, p = .030 and β = −.228, p = .045). No significant associations were found between the amount of treatments and TUG performance, flexion ROM, and extensor and flexor strength.
| TKA | 95 % Confidence Interval for B | UKA | 95 % Confidence Interval for B | |||||||||
| R2 | B | Lower limit | Upper limit | ß | p-value | R2 | B | Lower limit | Upper limit | ß | p-value | |
| Location of preoperative physiotherapy | ||||||||||||
| Functional mobility | ||||||||||||
| TUG (s) | −.003 | −.013 | ||||||||||
| Affiliated practice | .698 | −.478 | 1.874 | .109 | .242 | .291 | .677 | −1.091 | .046 | .677 | ||
| Not affiliated practice | −.192 | .822 | −1.883 | −.021 | .822 | −1.222 | .470 | −4.566 | −.079 | .470 | ||
| ROM | ||||||||||||
| Extension (°) | .041 | .027 | ||||||||||
| Affiliated practice | −3.557 | −6.200 | −.915 | −.241 | .009 | −1.945 | −3.941 | .051 | −.209 | .056 | ||
| Not affiliated practice | −.399 | −4.198 | 3.399 | −.019 | .836 | −2.878 | −7.658 | 1.902 | −.129 | .235 | ||
| Flexion (°) | −.004 | .009 | ||||||||||
| Affiliated practice | −.840 | −6.248 | 4.569 | −.028 | .759 | −1.327 | −6.620 | 3.967 | −.054 | .620 | ||
| Not affiliated practice | 4.202 | −3.572 | 11.976 | .099 | .287 | −10.552 | −23.229 | 2.124 | −.180 | .102 | ||
| Muscle strength | ||||||||||||
| Peak extension torque (Nm/kg) | ||||||||||||
| 60°/s | .022 | −.013 | ||||||||||
| Affiliated practice | 10.815 | −2.737 | 24.367 | .145 | .117 | −2.714 | −18.369 | 12.941 | −.038 | .731 | ||
| Not affiliated practice | −10.850 | −30.896 | 9.196 | −.098 | .286 | 14.478 | −23.186 | 52.143 | .084 | .447 | ||
| 180°/s | .001 | −.012 | ||||||||||
| Affiliated practice | 5.159 | −4.215 | 14.532 | .101 | .278 | .815 | −9.404 | 11.035 | .017 | .874 | ||
| Not affiliated practice | −4.674 | −18.539 | 9.191 | −.062 | .506 | 12.002 | −12.585 | 36.589 | .106 | .335 | ||
| Peak flexion torque (Nm/kg) | ||||||||||||
| 60°/s | −.009 | −.10 | −4.740 | −15.767 | 6.287 | −.093 | .395 | |||||
| Affiliated practice | 4.046 | −6.460 | 14.552 | .071 | .447 | 5.843 | −20.687 | 32.373 | .048 | .663 | ||
| Not affiliated practice | −3.066 | −19.097 | 12.965 | −.035 | .706 | |||||||
| 180°/s | −.011 | −.017 | ||||||||||
| Affiliated practice | 1.749 | −7.026 | 10.524 | .037 | .694 | −2.634 | −11.402 | 6.134 | −.066 | .552 | ||
| Not affiliated practice | −3.711 | −16.690 | 9.269 | −.053 | .572 | 3.008 | −18.087 | 24.102 | .031 | .777 | ||
| Amount of treatments | ||||||||||||
| Functional mobility | ||||||||||||
| TUG (s) | −.005 | −.017 | ||||||||||
| 1-10 treatment | .126 | −1.204 | 1.455 | .017 | .852 | −.052 | −1.543 | 1.440 | −.008 | .945 | ||
| >10 treatments | .797 | −.550 | 2.144 | .109 | .244 | .641 | 1.329 | 2.610 | .073 | .520 | ||
| ROM | ||||||||||||
| Extension (°) | .026 | .027 | ||||||||||
| 1-10 treatments | −3.340 | −6.345 | −.334 | −.202 | .030 | −2.209 | −4.363 | −.054 | −.228 | .045 | ||
| >10 treatments | −2.029 | −5.074 | 1.016 | −.121 | .190 | −1.628 | −4.441 | 1.186 | −.128 | .253 | ||
| Flexion (°) | −.015 | −.016 | ||||||||||
| 1-10 treatments | −.143 | −6.281 | 5.994 | −.004 | .963 | −2.206 | −7.989 | 3.578 | −.086 | .450 | ||
| >10 treatments | 1.239 | −4.980 | 7.458 | .037 | .694 | −2.017 | −9.570 | 5.536 | −.061 | .597 | ||
| Muscle strength | ||||||||||||
| Peak extension torque (Nm/kg) | ||||||||||||
| 60°/s | −.005 | −.023 | ||||||||||
| 1-10 treatments | 9.049 | −6.456 | 24.554 | .108 | .250 | −1.727 | −18.717 | 15.263 | −.023 | .840 | ||
| >10 treatments | 1.051 | −14.876 | 16.978 | .012 | .896 | .011 | −22.221 | 22.244 | .000 | .999 | ||
| 180°/s | −.009 | −.021 | ||||||||||
| 1-10 treatments | 4.911 | −5.722 | 15.545 | .086 | .362 | 1.159 | −9.928 | 12.247 | .024 | .836 | ||
| >10 treatments | .130 | −10.792 | 11.053 | .002 | .981 | 3.250 | −11.258 | 17.759 | .051 | .657 | ||
| Peak flexion torque (Nm/kg) | ||||||||||||
| 60°/s | −.011 | −.013 | ||||||||||
| 1-10 treatment | 4.706 | −7.321 | 16.733 | .073 | .440 | −5.460 | −17.386 | 6.467 | −.103 | .365 | ||
| >10 treatments | −.195 | −12.389 | 11.999 | −.003 | .975 | −.122 | −15.729 | 15.484 | −.002 | .988 | ||
| 180°/s | −.010 | −.006 | ||||||||||
| 1-10 treatments | 2.887 | −7.012 | 12.787 | .054 | .565 | −4.402 | −13.820 | 5.017 | −.105 | .355 | ||
| >10 treatments | −2.417 | −12.586 | 7.752 | −.044 | .639 | 2.893 | −9.432 | 15.218 | .053 | .642 | ||
Table 4 presents the associations between pre- and postoperative levels of physical functioning. All outcome measures demonstrate a significant association between pre- and postoperative levels, except for extension ROM in UKA patients (p = .178). Preoperative level of the TUG, together with age, predicts 28.9 % of the level one year after surgery (B = .341, 95%-CI .462 to .454) for TKA patients, and 32.1 % (B = .196, 95%-CI .088 to .303) for UKA patients. Extension strength and flexion strength at both velocities are predictive of the level after one year by more than 45 % for both groups.
| TKA | 95 % Confidence Interval for B | UKA | 95 % Confidence Interval for B | |||||||||
| R2 | B | Lower limit | Upper limit | ß | p-value | R2 | B | Lower limit | Upper limit | ß | p-value | |
| Functional mobility | ||||||||||||
| TUG (s) | .289 | .321 | ||||||||||
| T0 — TUG | .341 | .220 | .462 | .454 | <.001 | .196 | .088 | .303 | .346 | <.001 | ||
| Age | .053 | .003 | .104 | .170 | .039 | .078 | .035 | .121 | .341 | <.001 | ||
| ROM | ||||||||||||
| Extension (°) | .038 | .122 | .023 | .221 | .050 | .016 | .010 | .455 | −.211 | 1.121 | .147 | .178 |
| Flexion (°) | .093 | .284 | .132 | .436 | .316 | <.001 | .126 | .364 | .165 | .563 | .369 | <.001 |
| Muscle strength | ||||||||||||
| Peak extension torque (Nm/kg) | ||||||||||||
| 60°/s | .476 | .466 | ||||||||||
| T0 — 60°/s | .451 | .309 | .594 | .508 | <.001 | .495 | .316 | .674 | .541 | <.001 | ||
| Sex | −17.352 | −27.434 | −7.270 | −.276 | <.001 | −14.541 | −27.409 | −1.673 | −.221 | .027 | ||
| 180°/s | .604 | .516 | ||||||||||
| T0 — 180°/s | .582 | .458 | .706 | .660 | <.001 | .595 | .413 | .777 | .602 | <.001 | ||
| Sex | −8.226 | −14.226 | −2.225 | −.192 | .008 | −8.838 | −17.411 | −.265 | −.190 | .043 | ||
| Peak flexion torque (Nm/kg) | ||||||||||||
| 60°/s | .610 | .600 | ||||||||||
| T0 — 60°/s | .681 | .571 | .790 | .749 | <.001 | .568 | .410 | .726 | .603 | <.001 | ||
| Sex | −12.439 | −20.448 | −4.431 | −.261 | .003 | |||||||
| Age | −.429 | −.856 | −.002 | −.121 | .049 | |||||||
| 180°/s | .625 | .648 | ||||||||||
| T0 — 180°/s | .563 | .443 | .684 | .634 | <.001 | .570 | .417 | .722 | .609 | <.001 | ||
| Sex | −8.124 | −13.496 | −2.751 | −.202 | .003 | −7.952 | −13.866 | −2.039 | −.207 | .009 | ||
| Age | −.373 | −.706 | −.040 | −.132 | .029 | −.355 | −.691 | −.018 | −.149 | .039 | ||
4 Discussion
The study aimed to investigate the correlation between (regionally) standardized preoperative physiotherapy, as characterized by session quantity and location, and muscle strength, FM, and ROM prior to knee arthroplasty. Multivariate regression analyses found no significant associations between receiving standardized versus no or non-standardized physiotherapy and these outcomes, except for extension ROM in TKA patients. Similarly, no significant associations were observed between the number of preoperative physiotherapy sessions and outcomes, except for extension ROM for both TKA and UKA patients. Additionally, the study examined the correlation between pre- and postoperative muscle strength, FM, and ROM in knee arthroplasty patients, revealing significant relationships. Hence, preoperative functioning predicts postoperative outcomes, and based on this study, is irrespective of preoperative physiotherapy type or frequency.
Previous studies have shown the benefits of standardized care pathways for osteoarthritis with physiotherapy for knee OA patients.13,14 However, little was known about the impact of physiotherapy on physical functioning before knee arthroplasty surgery for severe knee OA patients. The present results show no significant associations between adherence to preoperative physiotherapy following (regionally) standardized physiotherapy and the level of physical functioning prior to knee arthroplasty surgery. Neither the location nor the amount of physiotherapy sessions was associated with muscle strength or functional mobility, but some correlations were observed with knee ROM. Previous research in the Netherlands has already demonstrated no difference in patient-reported outcome measures (PROMs) such as pain, physical functioning, self-efficacy, and active pain coping between patients who did and did not undergo stepped-care intervention after one year.29 However, they also noted a caveat applicable to this study: deviations from the stepped-care principle may sometimes be unavoidable or desirable due to limitations imposed by patients' health insurance coverage, despite the potential for optimal care. In addition to the possibility that this was also the case in the present study, it is also plausible that the lack of association between standardized preoperative physiotherapy and physical outcome measures may stem from the parsimonious method of querying this potential predictor. Specifically, participants were only asked whether preoperative physiotherapy was undergone, its location, and frequency. Not considered, for instance, were the timing of physiotherapy sessions and the specific exercises performed during these sessions. Nevertheless, the results of this study on the implementation of preoperative physiotherapy prior to knee arthroplasty are consistent with findings from prior studies5–11 as described in the Dutch OA guideline.30
Interestingly, the present results indicate a notable association between preoperative and postoperative levels of physical functioning. Linear regression analysis demonstrated that for TKA patients every second they were faster on the TUG preoperatively, they will be 1.341 s faster one year post-surgery. Since the MCID is 2.27 s,31 a patient who is 2 s faster preoperatively will surpass this threshold. Additionally, a higher preoperative ROM is significantly associated with a higher postoperative ROM, but the differences are clinically irrelevant. What this could also indicate is that delaying knee surgery, while allowing the patient's physical functioning to deteriorate further, may result in a knee prosthesis being unable to fully restore this lost function. This suggests that orthopedic care should not be indiscriminately postponed.
This “better in, better out” also seems to apply to muscle strength of the quadriceps and hamstrings in these patients. Indeed, we found significant associations between pre- and postoperative maximum strength and strength endurance outcomes. Previous research has established that a 20 % increase in peak torque at 60°/s can be deemed a true change in strength concerning knee extensor and flexor muscles.32 The outcomes indicate that extension strength at 60°/s increases by .451–.495 Nm/kg when it is 1.0 Nm/kg higher preoperatively. On average, this group is likely to exhibit a clinically relevant difference. The mean extension muscle strength at 60°/s in our study group at baseline was 86.2 Nm/kg, contrasting with values ranging from 46.23 to 55.71 Nm/kg reported in other studies.33,34 The fact that the muscle strength of the investigated population differs significantly from that of populations in other studies may potentially lower the generalizability of this study.
Several limitations warrant consideration in interpreting the findings of this study. First, recall bias is a concern as patients were asked about their preoperative physiotherapy at the time of the initial assessment, approximately three weeks before surgery. The lack of differentiation regarding the timing and content of these sessions, coupled with the potential for socially desirable or self-serving responses, introduces the risk of recall bias. Moreover, a significant portion of the initial patient group (n = 528) was excluded due to unreliable measurements (n = 164), potentially favoring patients with less pain and skewing the results. Varying levels of physical activity or lifestyle habits could introduce confounding bias, although age, sex, and weight were included as potential confounders. The absence of preoperative physiotherapy measurements prevents objective assessment of its trajectory before surgery. Additionally, the study did not examine the impact of standardized preoperative physiotherapy on delaying or canceling surgeries, focusing only on patients undergoing knee arthroplasty. Without baseline measurements, the effect of preoperative physiotherapy on physical functioning cannot be determined. The study population's generalizability is questionable, as muscle strength levels and length of hospital stay differed from those in previous studies,35,36 indicating a potentially less typical knee arthroplasty candidate population.
To mitigate information bias, trained physiotherapists conducted the physical tests. The involvement of approximately ten physiotherapists did not affect measurement reliability, as tests with acceptable to excellent inter-rater reliability were used. To address selection bias, all eligible patients within a feasible travel distance were invited to participate. A strength of this study is that it confirms previous findings, showing a disparity between PROMs and objectively measured physical functioning,37,38 and aligns with earlier research on the association between standardized preoperative physiotherapy and PROMs.29
For further research, it appears intriguing to differentiate the trajectories of various patient groups and identify the patient characteristics that predict outcomes following knee surgery. Identifying characteristics linked to physical functioning could potentially facilitate the application of more tailored care strategies, allowing for more targeted guidance and possibly enhanced support throughout the entire knee arthroplasty process for the appropriate patient population.
5 Conclusion
This study concludes that (standardized) preoperative physiotherapy is not significantly associated with physical functioning levels prior to surgery. The lack of baseline measurements before preoperative physiotherapy prevents determining its specific impact on physical functioning. However, a higher preoperative physical functioning level is associated with better physical functioning one year postoperatively for the cohort, although this trend may vary among different patient subgroups.
Author’s contributions statement
JB, DH, and LK conceived the research topic, after which TB and JB formulated the research question. TB and JB developed the methodology, with TB taking the lead. TB was responsible for data collection, while JB managed the data. TB took the lead in writing the manuscript, with JB serving as the supervisor. DH and LK contributed to the final revisions of the manuscript, providing oversight and supervision throughout the process. All the authors finally approved the manuscript. All authors have read and agreed to the published version of the manuscript.
Funding
The present study was conducted without external funding. There was no involvement of any funding sources in the study design, data collection, analysis, interpretation, or decision to publish.
Ethics
This study is classified as a non-WMO study; therefore, the study protocol did not require approval from an Institutional Review Board or Ethics Committee. Participants were informed about the study through written and verbal explanations, detailing the study's purpose, procedures, and their rights. Informed consent was obtained from all participants prior to their inclusion in the study, with consent being documented through signed consent forms.
Patient involvement statement
Study participants were not involved in the design, conduct, interpretation, or translation of the current research.
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